The assignee of the present invention manufactures and deploys spacecraft for, inter alia, communications and broadcast services from geosynchronous orbit, for example. Such spacecraft are commonly delivered to an initial non-operational (“parking” or “transfer”) orbit by a launch vehicle. An on-board propulsion subsystem including chemical and/or electric thrusters included in the spacecraft is typically used to accomplish orbit raising from the non-operational orbit to the geosynchronous (or other higher altitude) orbit.
Spacecraft must be compatible with significant dynamic loads during launch, including acceleration, vibration and acoustic environmental loads. Primary structure to enable the spacecraft to safely withstand such loads may include internally disposed load-bearing components. For example, referring to FIG. 1, a spacecraft 100 includes a central cylinder 101 configured to interface, near an aft portion 101 of the spacecraft 100, with a payload adapter ring of a launch vehicle upper stage (not illustrated). Bus and payload equipment of the spacecraft 100, omitted for clarity of illustration, may be supported by the central cylinder 101 either directly, by way of struts (not illustrated) or structural panels, such as panels 102, 103, 104. It may be observed that the panels 102 and 103 are generally parallel with a spacecraft yaw (Z) and that panel 104 is disposed generally orthogonal to the Z axis. Any of panels 102, 103 and 104 may carry bus or payload equipment. Moreover, as illustrated, the panels 102, 103 and 104 may be coupled to externally facing equipment panels such as panel 106, disposed generally orthogonal to the pitch (Y) axis, and panel 107, disposed generally orthogonal to the Z axis. It will be appreciated that launch loads associated with the equipment panels and equipment mounted thereon are all carried by the central cylinder 101.
Launch costs represent a significant fraction of the mission cost of a typical satellite. Accordingly an improved spacecraft structural arrangement that enables an increase in the amount of payload mass deliverable to the operational orbit for a given launch mass is desirable.